Below is from LMC Trucks.......which carries the Fog lights for the Chevy Silverado and GMC Sierra Trucks, the Fog Light for your 05" Sierra is at the Top Right of the picture......To Remove and Replace the Fog light, they are just held on with 2 Bolts, also make sure to Dis-Connect the Wiring......

With mine the assembly with the light is like a ball. It fits the back piece which is bolted to the truck. The problem is to replace the back piece.. I haven't had time to crawl under it again to check. Snow is coming!!!!!!!!!!

With mine the assembly with the light is like a ball. It fits the back piece which is bolted to the truck. The problem is to replace the back piece.. I haven't had time to crawl under it again to check. Snow is coming!!!!!!!!!!

Click to expand...

So the Fog light you have is the one in the 3rd picture down on the Right hand side of the picture above and your looking to replace the Mounting Bracket itself??......